1. Field of the Invention
Example embodiments relate in general to a method and apparatus for control of the three-dimensional movement of a mast. More specifically, example embodiments relate to control of the movement of nuclear reactor components, in terms of ensuring that their two-dimensional location (i.e., plant coordinate), their elevation, and their orientation (i.e., angle of rotation) correspond to a reactor engineer's instructions. Example embodiments further relate to a control permissive that allows reactor components to be picked-up and dropped-off in plant coordinates and orientations that match a reactor engineer move sheet during nuclear reactor refueling or initial start-up.
2. Related Art
In a Boiling Water Reactor (BWR) the orientation of reactor components such as fuel assemblies and blade guides (single or double blade) is important for various reasons. During operation of the reactor the fuel assemblies must be oriented for proper physics of the core. During maintenance and examination, single and double blade guides may be oriented to keep control rods in a vertical position while providing access for inspection.
Fuel assemblies and single blade guides may have four possible orientations (each at and angle of rotation of 90° increments) when they are lowered into the core or spent fuel pool. In addition to the orientation of the fuel assembly, another important consideration may be the location of the channel fastener. Fuel assemblies may be located in a quadrant of a fuel cell, and the fasteners must face the center of the cell. The single blade guide also has an orientation consideration, as buttons on the side of the blade must face the control rods in order for the blade to effectively hold the rods in a vertical position following placement of the blade into a cell. A double blade guide can be loaded in only two directions, depending on the maintenance or examination being conducted in the core.
Mis-orientation of reactor components may be a potentially time-consuming and expensive problem in the operation of nuclear reactors. Most US nuclear plants classify a fuel assembly in the wrong orientation as a fuel handling error, if the wrong orientation is in the core. A fuel handling error could cost a utility $1.5M on critical path time. Conventionally, the responsibility of fuel assembly orientation has been on human operators called the fuel mover and the spotter positioned on a refueling platform, to ensure that reactor components are relocated and oriented according to plant move sheets. Even with a second or third verifier, reactor components may be installed in the wrong orientation, leading to plant downtime or even serious reactor malfunction, potential accidents, and potential Nuclear Regulatory Commission (NRC) fines and investigation.